Basic propulsion assists for human-powered vehicles such as bicycles, tricycles, quadricycles and the like have been contemplated. In one known approach, a hub assembly on one or more of the wheels of a vehicle is replaced with a motor. In another approach, an extra wheel is attached to a particular vehicle via a static connector whereby the additional wheel is powered independently from the vehicle drivetrain. In both instances, the assist is meant to help propel the vehicle with less effort, hence the term “assist.”
In certain instances, it is not practical to use motors in place of hub assemblies on certain vehicles because some vehicles are not readily convertible from solely human-powered to propulsion-assisted. In other instances, because of the physical makeup of the wheel and/or vehicle, hub assemblies cannot be replaced with motors. Moreover, assists are not always required or desired for certain vehicular usage. When not being used, a hub based assist may increase the vehicular load by actually increasing the weight of the vehicle. In addition, use of an additional wheel attached to a vehicle may increase the rolling resistance of the vehicle.
A wheel attachment is needed that overcomes the above shortcomings.